The present invention relates generally to improvements in cameras with devices for electrically indicating information, and it relates more particularly to an improved power source switch device in a camera to control the power supply to an electrical indicating device.
Generally, cameras are provided with manually movable adjusting members, such as a diaphragm setting member, a shutter speed setting member, a distance setting member and a film speed setting member, for adjusting such photographic parameters and conditions as the amount of exposure and focusing. The cameras are further frequently provided with electrical indicating devices for indicating or exhibiting information on the exposure or focusing condition adjusted by any one of the adjusting members. The electrical indicating device exhibits or indicates the information, e.g. the diaphragm aperture value, shutter speed or whether the camera is so adjusted as to achieve the proper exposure at an appropriate place of the camera, e.g. in the viewfinder.
A number of power source switch devices have been proposed for controlling the power supply to the electrical indicating device. For instance, a device is known in which a switch member is provided between the indicating device and power source, and a manually operated member, such as a push button or lever, interlocked with the switch member is provided on the camera body, the switch member being opened and closed by operating the manually operated member.
With such device, however, the manually operated member must be operated without fail before the adjusting member is operated, thus rendering the camera awkward and troublesome to operate in preparation for performing photography and causing great inconvenience to the user.
Further, with such device, although the manually operated member must first be manually operated in preparation for the photography, the user who is inexperienced in the camera operation may overlook the required manual operation. This may lead to total failure in the preparatory photography operation or to an imperfect preparatory operation for performing the photography.
With such device, in addition, even if the user is familiar with the camera operation, he may fail from time to time to operate the manual operated member for closing the switch member. In such case, the user can recognize his failure to effect the manual operation by the absence of aforesaid indication, and after such recognition he may then effect the manual operation. When the switch member is closed in the above sequence, however, a considerable time is consumed in the initiation of preparatory operation for taking the photograph before which the power switch member is closed, and thus the device possesses the disadvantage that an important shutter opportunity for photographing a fast moving or continuously changing subject may be missed.
In an attempt to eliminate the above disadvantages, a device has been proposed in U.S. Pat. No. 3,741,089, issued on June 26, 1973, in which the manually operating member for closing the power switch is provided proximate to the related adjusting member.
The power source switch device disclosed by the U.S. Patent comprises a normally open switch for connecting the power source to the electrically indicating device and a manually operating member which is biased to project outside the camera body and which closes the normally open switch when depressed. The manually operated member is provided proximate to the adjusting member, such as a diaphragm setting member, and the manually operated member is depressed simultaneously with the adjusting member being touched by the user's finger when placed on the adjusting member for its manual operation.
With such a power source switch device, the manually operated member is operated in operative relation to the operation of the adjusting member, the device thus eliminating most of the aforesaid inconveniences.
With such power source switch device, however, the manually operated member may not be depressed in case the adjusting member is formed with a relatively large and wide operating portion with which the user's finger comes into contact. This results from the user's finger not protruding from the operating portion enough to depress the manually operated member when the user operates the adjusting member.
Accordingly, the above proposed power source switch device cannot be suitably employed unless the operating portion of the adjusting member is narrow so that the user's finger protrudes from the operating portion when the finger is placed thereon for moving the adjusting member. Therefore, the power source switch device disclosed by the above identified U.S. Patent cannot be employed in a camera having the comparatively large adjusting member to be operated, like the distance setting member for a single lens reflex camera.
In the device disclosed by the above identified U.S. Patent, the manually operated member is provided at a side of the adjusting member and the manually operated member is not operated when the adjusting member is operated from the other side where the manually operated member is not provided, the device thus often being inconvenient to use.
In addition, with the device disclosed by the above identified U.S. Patent, friction occurs between the manually operated member and the user's finger when the direction of the manually operated member's movement or the amount of its movement differs from that of the adjusting member, thus preventing the smooth operation of the adjusting member.
Furthermore, in the device disclosed by the above identified U.S. Patent, the manually operated member for operating the normally open switch and a spring for biasing the manually operated member to project from the camera body must be arranged within a particular space provided beside the adjusting member, and this causes an increase in the size of the camera, the device thus leading to additional inconvenience.